People grinning for photos on the white X, the approximate spot on Elm Street where President John F. Kennedy was shot in 1963; visitors standing on the infamous grassy knoll; fingers pointing toward the so-called sniper's perch on the sixth floor of the old Texas School Book Depository.

But there are few constants when it comes to the theories surrounding JFK's assassination. No detail is too large or too small to bicker over. Everyone's got an opinion.

Those theorists were out in force again Monday, 47 years after the president's death, to argue and reargue their points.

"There are crowds here every year," said Anthony Caglia, who takes a day off work to come down to the plaza each year. "You get all these different stories and theories from all kinds of people."

Some, though, just come to remember.

For Jim Stewart, walking on the grassy knoll was on his bucket list.

"I've just always been fascinated by it," said Stewart, who was visiting from Calgary. "I think so much of the United States would've been different if he lived."

Stewart, 55, said he remembers being herded into his elementary school's basement after the assassination and then being sent home and watching the aftermath on TV.

After making the trip to Dallas, Stewart said the scene was different than he imagined.

"Isn't there usually a moment of silence?" he asked, checking his cellphone clock.

That traditionally comes at 12:30 p.m. But during that time, John Judge was making a speech disputing the Warren Commission's assassination findings, which, among other things, concludes that Lee Harvey Oswald was the lone gunman.

Judge continued his speech until a young boy remarked, "That moment of silence was pretty loud."

Judge paused around 12:35 for a minute of quiet.

"This is a forum for crazies instead of reverence for what happened," Stewart said as he left the plaza.

For 13 years, Paul Noble has made the trip from Mansfield to join the crowds at Dealey Plaza. What he enjoys most year after year is the amalgam of theories.

"I talk to all kinds of people," said Noble, 52, as a man wandered past with a T-shirt that read: "Who Killed JFK?"

"They have all kinds of theories – that Oswald did it alone, that it was Lyndon Johnson, the CIA , Fidel Castro. Lots of different ideas."

Noble was 5 when Kennedy was shot. He doesn't remember the assassination, but he recalls seeing Jack Ruby shoot Oswald on an old black-and-white TV.

He's been intrigued ever since.

"I'll come here every year until I die," said Noble. "I can't wait till the 50th anniversary. There'll be lots of things going on, probably thousands of people. Maybe even some celebrities."

Standing near a portrait of Kennedy with six white carnations at the base, Tommy Sills still remembers that November day clearly.

He was 9 years old, standing with his father at the corner of Houston and Main streets. He had been allowed to leave school to watch the presidential motorcade.

Sills remembers the roar of the crowd as the car turned the corner.

"Then I thought I heard a motorcycle backfire and didn't think anything of it," said Sills, 57, of Irving. "But with the second shot, people started screaming and I watched the Secret Service agent crawling on the back of the limo."

Sills and his father left downtown right away. He said he had never seen his father that spooked. Curiously, as if nothing had happened, his dad dropped him back off at Otis Brown Elementary School in Irving.

Now a history teacher, Sills sometimes brings his students down to the plaza and gives them a firsthand lesson.